[TYPO3-dev] Override TCA with help of ext_tables.php in TYPO3 6.2

[Stefan Frömken]

Hello Dev-Team,

I want to override property "maxLevels" in treeConfig of tt_content:

$GLOBALS['TCA']['tt_content']['columns']['categories']['config']['treeConfig']['appearance']['maxLevels'] 
= 12;

I have cleared the cache, I have deleted the whole typo3temp-directory.
After a reload of the page I can found this entry in 
cache_core/ext_tables_sha1().php

But in BE -> Configuration -> TCA --> This entry was not found.

As I read there is no need to execute loadTCA anymore. So how to 
override TCA-Entries now?

Stefan